Abstract: In behavioral pharmacology, overall response rate is the measure most often used to
study the effects of drugs on an animal’s ongoing operant behavior. However, it has been argued
that an overall measure of response rate may not provide the most valid description of behavior
and, thus, a more detailed analysis might prove beneficial in classifying drug effects. The
purpose of the present research was to (1) study effects of methamphetamine on schedulecontrolled
responding, (2) determine if a log-survivor analysis recently used to study nose-poke
responding in rats could be extended for use with key-pecking in pigeons and (3) examine
microproperties of pigeon responding using an IRT analysis. Pigeons were trained to peck a
lighted key under a multiple random-interval (RI) 1-min, RI 4-min schedule. Interresponse times
(IRTs) were collected and then analyzed via log-survivor plots and an analysis described by
Blough (1963) and used in greater detail by Palya (1992). Log-survivor plots show the
proportion of IRTs greater than some time as a function of time in the session. The IRT analysis
involved graphing each individual IRT as a function of its temporal position within the interval.
Several doses of methamphetamine were administered (0.3 – 5.6 mg/kg) and the effect on both
summary measures (overall response rates) as well as the more detailed analyses was observed.
Log-survivor analyses did not produce the “broken-stick” responding seen in previous studies
with rats and quantitative measures of bout-initiations and within-bout responses could not be
obtained. The IRT plots showed clear bands of responding at 350 ms and 700 ms and responding
in the initial (350 ms) band was affected more than responding during other bands or at other
IRTs. These results strengthen the argument that not all responding (various IRTs) is uniformly
affected by methamphetamine administration and suggest that a detailed analysis of responding
might prove more useful than summary measures in characterizing drug effects on behavior.